[PATCH] slab: Error out on duplicate cache names when DEBUG_VM=y

[Pedro Falcato <pedro.falcato@gmail.com>]

Duplicate slab cache names can create havoc for userspace tooling that
expects slab cache names to be unique. This is a reasonable expectation.

Link: https://lore.kernel.org/linux-fsdevel/2d1d053da1cafb3e7940c4f25952da4f0af34e38.1722293276.git.osandov@fb.com/
Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com>
---
 mm/slab_common.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 40b582a014b..c4f31c887f9 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -88,6 +88,19 @@ unsigned int kmem_cache_size(struct kmem_cache *s)
 EXPORT_SYMBOL(kmem_cache_size);
 
 #ifdef CONFIG_DEBUG_VM
+
+static bool kmem_cache_is_duplicate_name(const char *name)
+{
+	struct kmem_cache *s;
+
+	list_for_each_entry(s, &slab_caches, list) {
+		if (!strcmp(s->name, name))
+			return true;
+	}
+
+	return false;
+}
+
 static int kmem_cache_sanity_check(const char *name, unsigned int size)
 {
 	if (!name || in_interrupt() || size > KMALLOC_MAX_SIZE) {
@@ -95,6 +108,12 @@ static int kmem_cache_sanity_check(const char *name, unsigned int size)
 		return -EINVAL;
 	}
 
+	if (kmem_cache_is_duplicate_name(name)) {
+		/* Duplicate names will confuse slabtop, et al */
+		pr_err("%s: name %s already exists as a cache\n", __func__, name);
+		return -EINVAL;
+	}
+
 	WARN_ON(strchr(name, ' '));	/* It confuses parsers */
 	return 0;
 }
-- 
2.46.0